SI-7933 REPL javax.script eval is cached result

The problem is that the repl underneath the script engine evaluates input to
val res0..resN, so it is a one shot operation. To allow repetition,
compile(script) now returns a CompiledScript object whose eval method can be
called any number of times.

src/compiler/scala/tools/nsc/util/package.scala

@@ -7,7 +7,7 @@ package scala
 package tools
 package nsc
 
-import java.io.{ OutputStream, PrintStream, ByteArrayOutputStream, PrintWriter, StringWriter }
+import java.io.{ OutputStream, PrintStream, ByteArrayOutputStream, PrintWriter, StringWriter, Reader }
 
 package object util {
   // forwarder for old code that builds against 2.9 and 2.10
@@ -46,6 +46,17 @@ package object util {
     (result, ts2 filterNot (ts1 contains _))
   }
 
+  def stringFromReader(reader: Reader) = {
+    val writer = new StringWriter()
+    var c = reader.read()
+    while(c != -1) {
+      writer.write(c)
+      c = reader.read()
+    }
+    reader.close()
+    writer.toString()
+  }
+
   /** Generate a string using a routine that wants to write on a stream. */
   def stringFromWriter(writer: PrintWriter => Unit): String = {
     val stringWriter = new StringWriter()

src/repl/scala/tools/nsc/interpreter/IMain.scala

@@ -18,7 +18,7 @@ import scala.reflect.internal.util.{ BatchSourceFile, SourceFile }
 import scala.tools.util.PathResolver
 import scala.tools.nsc.io.AbstractFile
 import scala.tools.nsc.typechecker.{ TypeStrings, StructuredTypeStrings }
-import scala.tools.nsc.util.{ ScalaClassLoader, stringFromWriter, StackTraceOps }
+import scala.tools.nsc.util.{ ScalaClassLoader, stringFromReader, stringFromWriter, StackTraceOps }
 import scala.tools.nsc.util.Exceptional.unwrap
 import javax.script.{AbstractScriptEngine, Bindings, ScriptContext, ScriptEngine, ScriptEngineFactory, ScriptException, CompiledScript, Compilable}
 
@@ -534,8 +534,7 @@ class IMain(@BeanProperty val factory: ScriptEngineFactory, initialSettings: Set
 
   var code = ""
   var bound = false
-  @throws[ScriptException]
-  def compile(script: String): CompiledScript = {
+  def compiled(script: String): CompiledScript = {
     if (!bound) {
       quietBind("engine" -> this.asInstanceOf[ScriptEngine])
       bound = true
@@ -562,18 +561,6 @@ class IMain(@BeanProperty val factory: ScriptEngineFactory, initialSettings: Set
     }
   }
 
-  @throws[ScriptException]
-  def compile(reader: java.io.Reader): CompiledScript = {
-    val writer = new java.io.StringWriter()
-    var c = reader.read()
-    while(c != -1) {
-      writer.write(c)
-      c = reader.read()
-    }
-    reader.close()
-    compile(writer.toString())
-  }
-
   private class WrappedRequest(val req: Request) extends CompiledScript {
     var recorded = false
 
@@ -1014,10 +1001,16 @@ class IMain(@BeanProperty val factory: ScriptEngineFactory, initialSettings: Set
   }
 
   @throws[ScriptException]
-  def eval(script: String, context: ScriptContext): Object = compile(script).eval(context)
+  def compile(script: String): CompiledScript = eval("new javax.script.CompiledScript { def eval(context: javax.script.ScriptContext): Object = { " + script + " }.asInstanceOf[Object]; def getEngine: javax.script.ScriptEngine = engine }").asInstanceOf[CompiledScript]
+
+  @throws[ScriptException]
+  def compile(reader: java.io.Reader): CompiledScript = compile(stringFromReader(reader))
+
+  @throws[ScriptException]
+  def eval(script: String, context: ScriptContext): Object = compiled(script).eval(context)
 
   @throws[ScriptException]
-  def eval(reader: java.io.Reader, context: ScriptContext): Object = compile(reader).eval(context)
+  def eval(reader: java.io.Reader, context: ScriptContext): Object = eval(stringFromReader(reader), context)
 
   override def finalize = close
 

test/files/run/t7843-jsr223-service.scala

@@ -0,0 +1,8 @@
+import scala.tools.nsc.interpreter.IMain
+
+object Test extends App {
+  val engine = new IMain.Factory getScriptEngine()
+  engine.asInstanceOf[IMain].settings.usejavacp.value = true
+  engine put ("n", 10)
+  engine eval "1 to n.asInstanceOf[Int] foreach print"
+}

test/files/run/t7933.check

@@ -0,0 +1,2 @@
+hello
+hello

test/files/run/t7933.scala

@@ -0,0 +1,11 @@
+import scala.tools.nsc.interpreter.IMain
+
+object Test extends App {
+  val engine = new IMain.Factory getScriptEngine()
+  engine.asInstanceOf[IMain].settings.usejavacp.value = true
+  val res2 = engine.asInstanceOf[javax.script.Compilable]
+  res2 compile "8" eval()
+  val res5 = res2 compile """println("hello") ; 8"""
+  res5 eval()
+  res5 eval()
+}